Transgenic animals

ABSTRACT

There is discloses a transgenic mouse over-expressing a potassium channel BEC1, which can be used as an effective tool for screening a substance for antidementia or a substance to improve learning and memory. 
     Also disclosed are an in vivo screening method of a substance for antidementia or a substance to improve learning and memory, which uses the learning and memory abilities of said mouse as the index, and an in vivo screening of a substance for antianxiety, which uses acceleration of anxiety as the index. 
     In addition, there is disclosed a method for producing a pharmaceutical composition for antidementia, learning and memory improvement use or antianxiety, using a substance capable of inhibiting the learning and memory potassium channel activity as the active ingredient which can be obtained by the aforementioned screening method of the present invention.

TECHNICAL FIELD

This invention relates to a model animal to be used as an effective tool for screening a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety, and a method for screening a novel substance for antidementia, substance to improve learning and memory or substance for antianxiety, which uses said model animal.

BACKGROUND OF THE INVENTION

Studies on the disorders in learning new information which occupies an important part of the mental activities of human and on the disorders in keeping and recalling already learned information are main themes for elucidating higher brain functions which have been regarded as the final frontier of life science. However, the cause for the disorders is unclear even at present and there are no sufficiently effective medicaments yet, so that early development of therapeutic drugs is greatly demanded. Even in the case of medicaments which have been reported to be effective in improving impairment in learning and memory of dementia patients to a certain degree, it has been pointed out that the duration of action is short and the clinically effective range is narrow (Feldman H. et al., (2001), Neurology, 57 (4), 613–20), that side effects such as hepatic toxicity and the like are generated (Summers W. K. et al., (1989), Lancet, 1 (8640), 729) and the like. In addition, for the purpose of finding an agent showing a useful therapeutic effect, it is necessary to take into consideration not only its in vitro efficacy but also in vivo bioavailability and transferring activity into the brain of the agent itself. Accordingly, the presence of a model animal which can be analyzed at individual level is essential for the elucidation of onset mechanism of the disease, prevention of onset of the disease or improvement of its pathologic condition, development of medicinal techniques for the treatment and of medicaments, and the like.

The transgenic mouse is expected as a method for displaying functions of genes in the living body for development of models for respective human diseases and development of various therapeutic drugs using these models. Including the c-myc oncogene-introduced transgenic mouse as a leukemia model which received a patent for a living life for the first time in the world (U.S. Pat. No. 5,087,571), various pathological model mice have been introduced, such as a prostatic hyperplasia mouse (U.S. Pat. No. 5,175,383), a diabetes mellitus-generating mouse (Japanese Patent 2771493), an Alzheimer'S disease model mouse (Games D. et al., (1995), Nature, 373 (6514), 523–7) and the like. Although many of the dementia-related transgenic animals represented by an APP transgenic show pathologic changes of dementia, it is difficult to detect impairment of learning and memory as a behavioral pattern in these animals, so that attempts have been made detect it by adding some factors such as aging and the like (Moran P. M. et al., (1995), Proc. Natl. Acad. Sci. USA, 92, 5341–5345; Hsiao K. et al., (1996), Science, 274, 99–102; Arendash G. W. et al., (2001), Brain Res., 891, 42–53). However, because preparation of such transgenic animals takes time, it was not practical to conveniently mass-prepare transgenic animals capable of detecting disorders of learning and memory as a behavioral pattern for use in the screening of a substance for antidementia.

Accordingly, demands have been directed toward a model animal to be used as an effective tool for screening a substance for antidementia or a substance to improve learning and memory, and a method for screening a substance for antidementia or a substance to improve learning and memory, which uses said model animal.

On the other hand, anxiety is a physiological phenomenon functioning as a warning against a present or potential danger. Anxiety becomes pathologic when it occurs without a real danger or its emotional strength intensifies. It is known that both of the physiological and pathological anxieties can threaten life when an organ disorder is generated in spite of its previous presence and may cause or permanently keep various physiological dysfunctions. There are various reports on transgenic animals as models of anxiety (Holmes A., (2001), Neurosci. Biobehav. Rev., 25 (3), 261–73). However, there is no applicable and optimum agent having less side effects even now.

Regarding a potassium channel BEC1 which can be used in preparing the transgenic animal of the present invention, the present inventors have disclosed it in WO 99/37677, and there are many reports regarding polynucleotides and polypeptides having a homology of from 98 to 99% with the BEC1 (WO 00/05346, WO 00/09534, WO 99/43696). However, a BEC1 transgenic animal was not prepared in reality, and its functions were not necessarily understood completely.

DISCLOSURE OF THE INVENTION

As a result of extensive studies, the present inventors have succeeded in preparing a transgenic mouse over-expressing the potassium channel BEC1 (Miyake A. et al., (1999), J. Biol. Chem., 274, 25018–25025) and found that, since the learning and memory abilities of said transgenic mouse is reduced, it can be used as a tool for screening a substance for antidementia or a substance to improve learning and memory. Also, it was found unexpectedly that, since anxiety of said transgenic mouse is accelerated, it can be used as a tool for screening a substance for antianxiety. In addition, an in vivo screening system for a substance for antidementia or a substance to improve learning and memory was constructed using the learning and memory abilities of said transgenic mouse as the index, and an in vivo screening system for a substance for antianxiety using the anxiety of said transgenic mouse as the index. As the results, the present invention was accomplished by providing a BEC1 transgenic animal as a model animal to be used as an effective tool for screening a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety, and a method for screening a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety, which uses said transgenic animal.

Accordingly, the present invention relates to,

(1) a transgenic animal introduced with a sequence comprising a promoter and a polynucleotide encoding a potassium channel which is a polypeptide consisting of the amino acid sequence represented by SEQ ID NO:2 or a polypeptide comprising an amino acid sequence in which from 1 to 10 of amino acids in the amino acid sequence represented by SEQ ID NO:2 are deleted, substituted and/or added,

(2) a transgenic animal which is a non-human animal or a offspring animal thereof obtained by effecting ontogenesis of a totipotent cell introduced, together with a promoter, with a polynucleotide encoding a potassium channel which is a polypeptide consisting of the amino acid sequence represented by SEQ ID NO:2 or a polypeptide comprising an amino acid sequence in which from 1 to 10 of amino acids in the amino acid sequence represented by SEQ ID NO:2 are deleted substituted and/or added, characterized in that the aforementioned polynucleotide is held on the chromosome and expresses said potassium channel in somatic cells,

(3) the transgenic animal described in (1) or (2), wherein it is obtained by effecting ontogenesis of a totipotent cell introduced, together with a promoter, with a polynucleotide encoding a potassium channel which is a polypeptide consisting of the amino acid sequence represented by SEQ ID NO:2 or a polypeptide which comprising an amino acid sequence in which from 1 to 10 of amino acids in the amino acid sequence represented by SEQ ID NO:2 are deleted substituted and/or added and is expressed limitedly to the brain,

(4) a transgenic animal introduced with a sequence comprising a promoter and a polynucleotide encoding a polypeptide which consists of an amino acid sequence having a homology of 90% or more with the amino acid sequence represented by SEQ ID NO:2 and is a potassium channel, or a offspring animal thereof obtained by effecting ontogenesis of a totipotent cell introduced, together with a promoter, with a polynucleotide encoding a polypeptide which consists of an amino acid sequence having a homology of 90% or more with the amino acid sequence represented by SEQ ID NO:2 and is a potassium channel, characterized in that the aforementioned polynucleotide is held on the chromosome and expresses said potassium channel in somatic cells,

(6) the transgenic animal described in (4) or (5), wherein it is obtained by effecting ontogenesis of a totipotent cell introduced, together with a promoter, with a polynucleotide encoding a potassium channel which is a polypeptide consisting of an amino acid sequence having a homology of 90% or more with the amino acid sequence represented by SEQ ID NO:2 and is expressed limitedly to the brain,

(7) the transgenic animal described in (1) to (6), wherein the promoter is a promoter capable of effecting expression of the potassium channel limitedly to the brain,

(8) the transgenic animal described in (1) to (7), wherein the promoter is an α-calcium-calmodulin-dependent kinase II promoter,

(9) the transgenic animal described in (1) to (8), wherein the non-human animal is a mouse,

(10), a method for detecting whether or not a substance to be tested inhibits said potassium channel, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), and -   a step of measuring learning and memory abilities,

(11) a method for detecting whether or not a substance to be tested inhibits said potassium channel, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), and -   a step of measuring anxiety,

(12) a method for detecting an anti-dementia effect or an improving effect on learning and memory, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), and -   a step of measuring learning and memory abilities,

(13) a method for detecting an anxiety inhibiting effect, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), and -   a step of measuring anxiety,

(14) a method for screening a substance for antidementia or a substance to improve learning and memory, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), a step of measuring learning and     memory abilities, and -   a step of selecting a substance having an anti-dementia effect or an     improving effect on learning and memory,

(15) a method for screening a substance for antianxiety, characterized in that it comprises

-   a step of administering a substance to be tested to the transgenic     animal described in (1) to (9), a step of measuring anxiety, and -   a step of selecting a substance having an anxiety inhibiting effect,

(16) a process for producing a pharmaceutical composition for antidementia or for improvement and therapy in learning and memory, characterized in that it comprises a step of carrying out screening using the screening method described in (14) and a step of making a pharmaceutical preparation using a substance obtained by the aforementioned screening, and

(17) a process for producing a pharmaceutical composition for anti-anxiety action, characterized in that it comprises

-   a step of carrying out screening using the screening method     described in (15) and a step of making a pharmaceutical preparation     using a substance obtained by the aforementioned screening.

Though there are many reports regarding polynucleotides and polypeptides having a homology of from 98 to 99% with the BEC1 which can be used in preparing the transgenic animal of the present invention (WO 00/05346, WO 00/09534, WO 99/43696), distinct use has not been elucidated for each of them. Also, though there are descriptions regarding transgenic animals in the aforementioned WO 00/05346 and WO 99/43696, their illustrative preparation methods are not described and there are no examples showing their actual preparation and no descriptions which support functions of said animals. On the other hand, the present inventors have disclosed on the BEC1 in WO 99/37677 in addition to the aforementioned pamphlets, but without descriptions regarding transgenic animals.

That is, the BEC1 transgenic animal, the method for screening a substance for antidementia, a substance to improve learning and memory and/or a substance for antianxiety, which uses said model animal, and the method for producing a pharmaceutical composition for antidementia, for improvement of learning and memory and/or antianxiety, described in the instant application, are inventions accomplished for the first time by the present inventors.

Regarding most of the transgenic animals other than the BEC1 counterpart, which have so far been reported on their ability to show a behavioral pattern of impairment in learning and memory, it was necessary to add some factors such as aging and the like for the detection of the disorders (Moran P. M. et al., (1995), Proc. Natl. Acad. Sci. USA, 92, 5341–5345; Hsiao K. et al., (1996), Science, 274, 99–102; Arendash G. W. et al., (2001), Brain Res., 891, 42–53), but preparation of such transgenic animals costs and takes time, and it was not practical to conveniently mass-prepare and use a transgenic animal capable of detecting impairment in learning and memory as a behavioral pattern for use in the screening of a substance for antidementia. Since the BEC1 transgenic animal described in the instant application shows a behavior of impairment in learning and memory at a young stage, it can be prepared conveniently and at a low cost and used in the screening of a substance for antidementia.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a result of an electrophoresis of PCR products obtained by carrying out PCR using a genomic DNA as the template isolated from the tail of an infant mouse in order to identify the transgenic mouse. N indicate a negative control (mouse genomic DNA, 338 bp) and P indicate a positive control (transgene, 245 bp).

FIG. 2 is a graph showing expressed amounts of BEC1 mRNA in the forebrain and cerebellum of F1 transgenic mice (# 6-2, # 7-3, # 6-5, # 7-7 and # 9-5) and a wild type (Wt) mouse.

BEST MODE FOR CARRYING OUT THE INVENTION

The terms to be used in the present invention are described.

The term “potassium channel” as used herein means a “potassium channel protein”, and the term “BEC1” means a “BEC1 protein”. The term “learning” as used herein means to acquire information from the external world, and the term “memory” includes preservation and regeneration of the information acquired by the leaning, and the process. The term “learning and memory” shows both concepts of “learning” and “memory”, and the term “memorizing and learning ability” means the ability to acquire, preserve and regenerate the outside information.

The term “transgene” means a gene for transgenic animal preparation use, which contains a polynucleotide encoding a promoter region and a potassium channel.

The following describes the present invention in detail.

[1] Polynucleotide Contained in the Transgene for Use in the Preparation of the Transgenic Animal of the Present Invention and Polypeptide Encoded by Said Polynucleotide

The potassium channel polypeptide encoded by the polynucleotide contained in the transgene for use in the preparation of the transgenic animal of the present invention includes

-   (1) a polypeptide consisting of the amino acid sequence represented     by SEQ ID NO:2, -   (2) a polypeptide comprising an amino acid sequence in which from 1     to 10 of amino acids in the amino acid sequence represented by SEQ     ID NO:2 are deleted substituted and/or added and is a potassium     channel (to be referred to as functionally equivalent modified one     hereinafter), and -   (3) a polypeptide which consists of an amino acid sequence having a     homology of 90% or more with the amino acid sequence represented by     SEQ ID NO:2 and is a potassium channel (to be referred to as     homologous polypeptide hereinafter).

As the functionally equivalent modified one, “a polypeptide which comprising the amino acid sequence represented by SEQ ID NO:2 and is a potassium channel”, “a polypeptide which consists of an amino acid sequence in which from 1 to 10, preferably 1 to 7, more preferably 1 to 5, of amino acids in the amino acid sequence represented by SEQ ID NO:2 are deleted substituted and/or inserted and is a potassium channel” or “a polypeptide which consists of an amino acid sequence in which from 1 to 10, preferably 1 to 7, more preferably 1 to 5, of amino acids in the amino acid sequence represented by SEQ ID NO:2 are deleted substituted and/or inserted and is a potassium channel which is expressed limitedly to the brain” is desirable, and the “polypeptide which comprising the amino acid sequence represented by SEQ ID NO:2 and is a potassium channel” is more desirable.

Though the homologous polypeptide is not particularly limited, with the proviso that it consists of an amino acid sequence having a homology of 90% or more with the amino acid sequence represented by SEQ ID NO:2 and is a potassium channel, it can consist of an amino acid sequence having a homology of preferably 95% or more, more preferably 98% or more, with the amino acid sequence represented by SEQ ID NO:2 and is preferably a potassium channel which is expressed limitedly to the brain. In this connection, the aforementioned term “homology” as used herein means a value obtained by using parameters prepared as default by Clustal program (Higgins and Sharp, Gene, 73, 237–244, 1998; Thompson et al., Nucleic Acid Res., 22, 4673–4680, 1994) retrieval. The aforementioned parameters are as follows. As Pairwise Alignment Parameters,

K tuple 1 Gap Penalty 3 Window 5 Diagonals Saved 5

The polypeptide encoded by the polynucleotide contained in the transgene for use in the preparation of the transgenic animal of the present invention has been described in the foregoing, and the polypeptide consisting of the amino acid sequence represented by SEQ ID NO:2, the functionally equivalent modified body thereof and the homologous polypeptide thereof are generally referred to as “learning and memory potassium channel”. The “learning and memory potassium channel” represents a “learning and memory potassium channel protein”. A protein as the polypeptide consisting of the amino acid sequence represented by SEQ ID NO:2 is called BEC1.

In addition, the polynucleotide having a nucleotide sequence encoding the learning and memory potassium channel may be any polynucleotide with the proviso that it is a polynucleotide consisting of a nucleotide sequence encoding a polypeptide represented by the amino acid sequence described in SEQ ID NO:2, a functionally equivalent modified body thereof or a homologous polypeptide thereof. It is preferably a polynucleotide consisting of a nucleotide sequence encoding the amino acid sequence described in SEQ ID NO:2, more preferably the nucleotide sequence described in SEQ ID NO:1.

[2] Method for Preparing Transgenic Animal Characterized in that it Expresses Learning and Memory Potassium Channel

A polynucleotide encoding a learning and memory potassium channel contained in a transgene can be obtained in accordance with the method described in WO 99/37677. For example, the BEC1 gene described in SEQ ID NO:1 can be prepared by a method in which an oligonucleotide is synthesized based on a nucleotide sequence of an optional part of a known sequence (WO 99/37677), and a human cDNA library is screened using this as a probe, or by synthesizing an oligonucleotide which hybridizes with both termini of the cDNA fragment of interest, and preparing it by the reverse transcriptase-polymerase chain reaction (RT-PCR method) using this as a primer from mRNA isolated from a human cell. In addition, a promoter sequence and an enhancer sequence for controlling expression of the potassium channel are linked to the transgene. By selecting this promoter/enhancer sequence, said potassium channel can be systemically expressed and can be selectively expressed in a specified tissue. Regarding the promoter, though not particularly limited, the promoter region of an α-calcium-calmodulin-dependent kinase II (α-CaM-kinase II) gene (Mayford, M. et al. (1990), Proc. Natl. Acad. Sci. USA, 93, 13250–13255), the promoter region of a neuron-specific enolase (Quon, D. et al. (1991), Nature, 352, 239–241), the promoter region of a Thy-1 gene (Vidal, M. et al. (1990), EMBO J., 9, 833–840) or the like can be used, the use of the promoter region of an α-calcium-calmodulin-dependent kinase II gene is desirable. Since the α-calcium-calmodulin-dependent kinase II gene is brain-selective and particularly it is a neuronal gene having high expression selectivity to the forebrain, a gene of interest can be expressed selectively in the brain, particularly in the forebrain (cerebral cortex and hippocampus), by the use of said promoter.

More illustratively, a transgene for use in the preparation of the transgenic animal of the present invention can be obtained by the method described in Example 1. As the transgene for use in the preparation of the transgenic animal of the present invention, a gene in which a BEC1 cDNA having a 5′ intron and poly(A) addition signal is linked to a downstream of the promoter region of α-calcium-calmodulin-dependent kinase II gene can for example be cited. Though the production method of said transgene is not particularly limited, a method which uses the polymerase chain reaction (Saiki, R. K. et al. (1988), Science, 239, 487–491; to be referred to as PCR hereinafter) can for example be cited. In addition, the gene manipulation techniques of the present invention can be carried out in accordance with known methods (e.g., Maniatis, T. et al., “Molecular Cloning—-A Laboratory Manual”, Cold Spring Harbor Laboratory, NY, 1982).

Firstly, for the preparation of the promoter region of α-calcium-calmodulin-dependent kinase II gene, a set of primers, such as SEQ ID NO:3 and SEQ ID NO:4, which can amplify the DNA of the present invention are designed based on the information of each nucleotide sequence represented by a sequence (Accession No. AJ222796) registered in a gene data base GenBank.

A part of said transgene can be obtained by carrying out PCR using the thus designed aforementioned primer set and a genomic DNA as the template. As the genomic DNA, a commercially available product (mfd. by Clontech) can be used, or it can be obtained from an animal blood sample using a commercially available genomic DNA extraction kit (mfd. by QIAGEN). In addition, α-calcium-calmodulin-dependent kinase II promoter region can be obtained by integrating the thus obtained DNA into an appropriate vector.

On the other hand, the polynucleotide encoding said potassium channel can be obtained in the following manner, it is not limited to this method and can be obtained also by the method described in WO 99/37677.

A mRNA sample including the one encoding said potassium channel is extracted by a known method from a cell or tissue, for example, the human brain, having an ability to produce said potassium channel. As the extraction method, the guanidine thiocyanate hot phenol method, the guanidine thiocyanate-guanidine hydrochloride method and the like can be exemplified, but the guanidine thiocyanate cesium chloride method can be cited as a desirable method. The cell or tissue having the ability to produce said potassium channel can be specified by a northern blotting method which uses a gene having a nucleotide sequence encoding said potassium channel or a part thereof or a western blotting method which uses an antibody specific for said potassium channel.

Purification of the mRNA can be carried out in accordance with a conventional method; for example, it can be purified by effecting adsorption of the mRNA to an oligo(dT) cellulose column and then eluting the same. As occasion demands, the mRNA can be further fractionated by a sucrose density gradient centrifugation or the like method. In addition, a commercially available already extracted mRNA can also be used without carrying out extraction of the mRNA.

Next, a single-stranded cDNA is synthesized by carrying out a reverse transcriptase reaction of the thus purified mRNA in the presence of a random primer or an oligo(dT) primer. This synthesis can be carried out by a conventional method. The potassium channel DNA of interest is amplified by carrying out PCR using the thus obtained single-stranded cDNA and two primers sandwiching a partial region of the gene of interest. The thus obtained DNA is fractionated by an agarose gel electrophoresis or the like. As occasion demands, a DNA fragment of interest can also be obtained by digesting the aforementioned DNA with restriction enzymes and the like and ligating the fragments.

Regarding the transgene for use in the preparation of the transgenic animal of the present invention, the arrangment order of the polynucleotides encoding the promoter and the learning and memory potassium channel is not particularly limited, as long as it contains at least an arbitrary promoter region and a polynucleotide encoding the learning and memory potassium channel, and the polynucleotide encoding the learning and memory potassium channel is arranged in such a manner that it is set under control of the promoter activity. As described in Example 1, the transgene for use in the preparation of the transgenic animal of the present invention can be prepared by transferring the aforementioned promoter region and the learning and memory potassium channel gene successively to multi-cloning sites of an appropriate vector. As the aforementioned vector, pUC18 (mfd. by Toyobo) can for example be cited.

The transgenic animal of the present invention is not particularly limited, as long as said transgene is introduced and the learning and memory potassium channel is over-expressed, but it can be prepared, for example, based on a conventionally known method (e.g., Animal Biotechnology, 1, 175–84, 1990) except that said transgene is used as the gene to be introduced. Illustratively, it can be prepared based, for example, on the procedure described in Example 1 which is described later. That is, a transgenic animal of interest can be prepared by introducing the aforementioned transgene into a totipotent cell of a non-human animal, allowing this cell to develop into individuals and then selecting an individual in which the transgene is integrated into the genome of somatic cell. The term “animal” as used herein means an animal excluding human (namely, non-human animal), and its examples include mammals other than human (e.g., rat, mouse, dog, cat, monkey, pig, cattle, sheep, rabbit, goat, dolphin or horse), birds (e.g., domestic fowl or quail), the amphibia (e.g., frog), the reptiles, insects (e.g., Drosophila) and the like. As the non-human animal, technically it is possible to use all animal species, but a mouse is particularly desirable, because a large number of inbred strains are created and, what is more, fertilized egg culturing, in vitro fertilization and the like techniques are well established. As the totipotent cell into which a gene is introduced, a fertilized egg or early stage embryo can be used in the case of mouse. In addition, physical injection (microinjection) of DNA is desirable as the method for introducing the gene into a cultured cell, when the production efficiency of transgenic animal individuals and the transferring efficiency of the transgene to the next generation are taken into consideration.

For example, a vector dissolved in HEPES buffer, phosphate buffer, physiological saline or the like is injected into a fertilized egg, and this egg is transplanted into the womb of a host animal treated with a hormone (PGF₂α, hCG, estradiol, LH or the like) or, in the case of a small animal, of an individual treated by a physical stimulation, for inducing into a condition of pseudopregnancy. By feeding this host animal and allowing it to carry out delivery, a gene-transferred non-human animal is obtained. Whether nor not a gene-transferred non-human animal is obtained can be known by extracting DNA from a part of the body (e.g., tail tip) and verifying the presence of the transgene by the Southern analysis or PCR. When an individual in which the presence of the transgene was confirmed is used as the founder, the transgene is transferred to 50% of its offspring, so that it is possible to prepare a wild type or mutation type animal efficiently.

The transgenic animal prepared in this manner is useful for a method for screening an agent targeted said channel, a method for detecting an anti-dementia effect or learning and memory improving effect, a method for detecting an anxiety inhibitory effect, a method for screening a substance for antidementia or a substance to improve learning and memory, and a method for screening a substance for antianxiety.

Although the substance to be tested which is used in the screening method of the present invention is not particularly limited, its examples include commercially available compounds (including peptides), various conventionally known compounds (including peptides) registered in Chemical File, a group of compounds obtained by the combinatorial chemistry techniques (N. K. Terrett, M. Gardner, D. W. Gordon, R. J. Kobylecki and J. Steele, Tetrahedron, 51, 8135–37, (1995)), microbial culture supernatants, natural components derived from plants and marine organisms, animal tissue extracts, and compounds (including peptides) prepared by chemically or biologically modifying the compounds (including peptides) selected by the screening method of the present invention.

[3] Method for Measuring Memorizing and Learning Ability and Method for Detecting (Screening) Substance to Improve Learning and Memory

The method for measuring memorizing and learning ability and method for detecting (screening) substance to improve learning and memory are described in the following. By the following methods for measuring memorizing and learning ability, whether or not a compound to be tested inhibits the learning and memory potassium channel can be detected.

1. A Method which Uses a Passive Avoidance Test

The anti-dementia effect and improvement effect on learning and memory can be detected through the measurement of the memorizing and learning ability by a passive avoidance test. The passive avoidance test can be carried out according to McGaugh J. L. (1966), Science, 153, 1351–1358, more illustratively by the method described in Example 5. Each compound to be tested is administered before the start of training (e.g., before 15 to 30 minutes) on the first day of the test. When the latency to enter the dark box of the test compound-administered group is prolonged in comparison with the vehicle-administered group, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as a substance for antidementia or a substance to improve learning and memory. In this connection, the vehicle-administered group means a group to which the vehicle of test compound (e.g., 0.5% methyl cellulose physiological saline or the like) alone was administered.

2. A Method Which Uses a Morris Water Maze Test

The anti-dementia effect and learning and memory improvement effect can be detected through the measurement of the memorizing and learning ability by a method which uses a Morris water maze test. This can be carried out as described in Example 4 in accordance with the method of Wenk G L et al. (1997), Learning and Memory. In Current Protocols in Neuroscience, New York, pp.8.5A. 1–8.5B. 7. Each compound to be tested is administered before the training (e.g., before 0 to 30 minutes) on each day. When the escepe latency to the platform in the test compound-administered group on and after the 2nd day is shortened in comparison with the vehicle-administered group, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as a substance for antidementia or a substance to improve learning and memory.

3. A Method which Uses a Sound-clued Fear Conditioning

The anti-dementia effect and learning and memory improvement effect can be detected through the measurement of the memorizing and learning ability by a method which uses a sound-clued fear conditioning. This can be carried out in accordance with the method of Wehner J M et al. (1997), Nature Genetics, 17, 331–334. A sound stimulus (5 kHz for 10 seconds) is produced to a transgenic mouse and a constant current stimulus (0.5 mA for 1 second) is added immediately thereafter. Each compound to be tested is administered 30 minutes before the provision of sound and electricity stimuli. After 24 hours, the sound stimulus alone is produced to the mouse, and freezing time of the mouse is measured for 5 minutes. When the immovable period of time is prolonged in comparison with the vehicle-administered group, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as-a substance for antidementia or a substance to improve learning and memory.

4. A Method which Uses Object Recognition Task

The anti-dementia effect and learning and memory improvement effect can be detected through the measurement of the memorizing and learning ability by a method which uses an object recognition task. This can be carried out in accordance with the method of Ennaceur A and Delacour J (1988), Behavior Brain Research, 31, 47–59. After standing still two identical objects inside a 60 cm square field, a transgenic mouse is put into the field and allowed to make a search inside the field freely for 5 minutes. Each test compound is administered 1 hour before putting the mouse into the field. One hour thereafter, one of the two objects is replaced by a different new object, and the mouse is again allowed to make a search inside the field for 5 minutes. A difference between the searching time for the new object and the searching time for the old object is used as the index of memory retention, and when this difference is prolonged in the test compound-administered group, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as a substance for antidementia or a substance to improve learning and memory.

5. A Method which Uses an Eyeblink Conditioning

The anti-dementia effect and learning and memory improvement effect can be detected through the measurement of the memorizing and learning ability by a method which uses an eyeblink conditioning. The mouse eyeblink conditioning can be carried out in accordance with the method of Chen L et al. (1996), Journal of Neuroscience, 16, 2829–2838. An electrode is embedded into the eyelid muscle of a transgenic mouse to record electromyogram of the eyelid muscle. A sound stimulus (5 kHz for 2 seconds) is produced to the mouse and an electric stimulus is added immediately thereafter from the embedded electrode to induce a blink in the mouse. The sound-electric stimuli are produced 50 times a day, and this training is carried out continuously 7 days. Each compound to be tested is administered every day 1 hour before the provision of stimuli. The frequency of generation of the eyelid muscle activity after the sound stimulus provision and before the electric stimulus provision is used as the index of the conditioned memory acquisition. When the frequency of generation of the eyelid muscle activity in the test compound-administered group exceeds that of the vehicle-administered group on and after the 2nd day of the start of the training, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as a substance for antidementia or a substance to improve learning and memory.

6. A Method which Uses Long-term Potentiation (LTP) in Hippocampus CA1 as the Index

The anti-dementia effect and learning and memory improvement effect can be detected through the measurement of the memorizing and learning ability by a method which uses long-term potentiation (LTP) in hippocampus CA1 as the index. The LTP in hippocampus CA1 can be carried out according to Tsien, J Z et al. (1996), Cell, 87, 1327–1338 or Oka H et al. (1999), J. Neurosci. Methods, 93, 61–67 or the like, more illustratively by the method described in Example 7. Each compound to be tested is applied before the tetanus stimulation (e.g., before 15 to 30 minutes). When the LTP at the time of the test compound addition is accelerated in comparison with the case of the vehicle addition, it can be judged that the compound has an anti-dementia effect or a learning and memory improvement effect. The test compound having an anti-dementia effect or a learning and memory improvement effect can be selected as a substance for antidementia or a substance to improve learning and memory.

[4] Measuring Method of Anxiety and Detection Method of Substance for Antianxiety

Measuring method of anxiety and detection method of a substance for antianxiety are exemplified in the following. By the following anxiety measuring methods, whether or not a compound to be tested inhibits the learning and memory potassium channel can be detected.

1. A Method which Uses a Light/Dark Exploration Test

The anxiety controlling effect can be detected through the measurement of anxiety by a method which uses a light/dark exploration test. This can be carried out as described in Example 6 in accordance with the method of Crawly J N et al. (1997), Current Protocols in Neuroscience, Wiley, New York. Administration of each compound to be tested is carried out 30 minutes before the start of the test. When the time spent in the light box or number of transitions between the light and dark box in the test compound-administered group exceeds that of the vehicle-administered group, it can be judged that the compound has an anxiety controlling effect. The test compound having an anxiety controlling effect can be selected as a substance for antianxiety.

2. In addition to this, the anxiety controlling effect can be detected through the measurement of anxiety by a conflict test (Carlini et al., (1978), Mod. Probl. Pharmacopsychiatry, 13, 80–102), an elevated plus maze (Handley S L and Mithani S (1984), Naunyn-schmiedeberg's Archive of Pharmacology, 327, 1–5) and the like. When improvement is found in the scores by these methods after administration of a compound to be tested to a transgenic mouse, it can be judged that the compound has an anxiety controlling effect. The test compound having an anxiety controlling effect can be selected as a substance for antianxiety.

[5] Production Method of Pharmaceutical Composition for Anti-dementia, Learning and Memory Improvement and Treatment or Anti-anxiety

Medicaments can be obtained using, as the main component, a substance capable of inhibiting the learning and memory potassium channel activity, which is selected by the screening method of the present invention. These medicaments are useful as a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety.

The pharmaceutical preparation which contains a substance capable of inhibiting the learning and memory potassium channel activity as the active ingredient can be prepared by using carriers, fillers and/or other additive agents generally used in preparing medicaments, in response to the type of the active ingredient. Examples of the administration include oral administration by tablets, pills, capsules, granules, fine subtilaes, powders, solutions for oral use and the like and parenteral administration by intravenous, intramuscular or the like injections, suppositories, percutaneous preparations, transmucosal preparations and the like. Particularly in the case of peptides which are digested in the stomach, intravenous injection or the like parenteral administration is desirable.

The solid composition for oral administration according to the present invention can be prepared by mixing one or more active substances with at least one inert diluent such as lactose, mannitol, glucose, microcrystalline cellulose, hydroxypropylcellulose, starch, polyvinyl pyrrolidone, aluminum magnesium silicate or the like. In the usual way, the aforementioned solid composition may contain other additives than the inert diluent, such as a lubricant, a disintegrating agent, a stabilizing agent, a solubilizing agent, a solubilization assisting agent and the like. If necessary, tablets or pills may be coated with a sugar coating or a film of a gastric or enteric substance. The liquid composition for oral administration includes, for example, emulsions, solutions, suspensions, syrups or elixirs and can contain a generally used inert diluent such as purified water or ethanol. In addition to the inert diluent, the aforementioned liquid composition can contain other additive agent such as a moistening agent, a suspending agent, a sweetener, an aromatic or an antiseptic.

The injections for parenteral administration can include aseptic aqueous or non-aqueous solutions, suspensions or emulsions. As a diluent, the water-soluble aqueous solutions or suspensions can include distilled water for injection, physiological saline or the like. As the diluent of the non-aqueous solutions or suspensions, it can include, for example, plant oil (e.g., propylene glycol, polyethylene glycol or olive oil), alcohols (e.g., ethanol), polysorbate 80 or the like. The aforementioned composition can further contain a moistening agent, an emulsifying agent, a dispersing agent, a stabilizing agent, a solubilizing agent, a solubilization assisting agent, an antiseptic or the like. The aforementioned composition can be sterilized, for example, by filtration through a bacteria retaining filter, blending of a germicide or irradiation. Alternatively, it can be used by firstly making into a sterile solid composition and dissolving it in sterile water or a sterile solvent for injection prior to its use.

Dose of the medicament containing, as the active ingredient, a substance capable of inhibiting the learning and memory potassium channel activity, which is selected by the screening method of the present invention, can be optionally decided by taking into consideration strength of the activity of the active ingredient selected by the aforementioned screening method, and symptoms, age, sex and the like of each patient to be treated.

EXAMPLES

The following describes the present invention in detail based on examples, but the present invention is not restricted by said examples. In this connection, unless otherwise noted, gene manipulation techniques can be carried out in accordance with the conventionally known methods (Maniatis, T. et al. (1982): “Molecular Cloning—A Laboratory Manual”, Cold Spring Harbor Laboratory, NY and the like). Also, when commercially available reagents and kits are used, they can be used in accordance with the instructions attached to the commercial products.

Example 1 Construction of Transgene for BEC1-overexpressing Transgenic Mouse

The transgene for production of a transgenic mouse overexpressing BEC1 having the amino acid sequence described in SEQ ID NO:2 comprises a gene in which a BEC1 cDNA (SEQ ID NO:1) with a 5′ intron and poly(A) addition signal is linked to a downstream of the promoter region of α-calcium-calmodulin-dependent kinase II gene.

The promoter region of α-calcium-calmodulin-dependent kinase II was obtained as two fragments having a mutually overlapping region, by PCR using a C57BL/6 mouse genomic DNA as the template. The C57BL/6 mouse genomic DNA was purified from a blood sample of the same mouse using a genomic DNA extraction kit (QIAamp DNA Blood Midi Kit, mfd. by QIAGEN). Primers were designed based on the sequence registered in a gene data base GenBank (Accession No. AJ222796). A gene fragment of 4.6 kb was obtained using an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:3 as the forward primer and using an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:4 as the reverse primer. An AatII recognition sequence is added to the 5′ terminal side of the aforementioned forward primer. In addition, a gene fragment of 3.7 kb was obtained using an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:5 as the forward primer and using an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:6 as the reverse primer. A SalI recognition sequence is added to the 5′ terminal side of the aforementioned reverse primer. Each PCR was carried out using a DNA polymerase (Pfu Turbo, mfd. by Stratagene) by employing a thermal denaturation at 99° C. (1 minute) and subsequent repetition of 45 cycles each comprising 99° C. (15 seconds), 58° C. (15 seconds) and 75° C. (10 minutes), or a thermal denaturation at 95° C. (1 minute) and subsequent repetition of 40 cycles each comprising 95° C. (15 seconds), 62° C. (15 seconds) and 75° C. (8 minutes), and the thus obtained gene fragment was cloned into a cloning vector (pCR-XL-TOPO plasmid, mfd. by Invitrogen). An endogenous XmaI recognizing sequence is present in the overlapping region of the 4.6 kb fragment and 3.7 kb fragment. The 4.6 kb fragment was digested with restriction enzymes AatII and XmaI, and the 3.7 kb fragment was digested with restriction enzymes XmaI and SalI. The thus obtained respective fragments were ligated and cloned into a plasmid pUC18 (mfd. by Toyobo) making use of the AatII and SalI recognition sequences. The α-calcium-calmodulin-dependent kinase II promoter region of interest was obtained by the above operation.

On the other hand, the BEC1 cDNA (SEQ ID NO:1) was obtained as a fragment containing a 5′ intron and poly(A) addition signal by PCR using a potassium channel expression vector pME-E1 (described in WO 99/37677) as the template. An oligonucleotide of the nucleotide sequence represented by SEQ ID NO:7 was designed as the forward primer, and an oligonucleotide comprising the nucleotide sequence represented by SEQ ID NO:8 as the reverse primer, respectively from the upstream sequence of 5′ intron and downstream sequence of poly(A) addition signal. A SalI recognition sequence is added to the aforementioned forward primer, and KpnI and NotI recognizing sequences to the reverse primer. PCR was carried out using a DNA polymerase (Pfu Turbo, mfd. by Stratagene) by employing a thermal denaturation at 96° C. (1 minute) and subsequent repetition of 30 cycles each comprising 96° C. (15 seconds), 60° C. (15 seconds) and 75° C. (8 minutes). The thus obtained 3.7 kb fragment was cloned into a cloning vector (pCR-XL-TOPO plasmid, mfd. by Invitrogen). This fragment was subcloned into a plasmid pUC18 (mfd. by Toyobo) making use of the SpeI recognition sequence and KpnI recognition sequence, and the aforementioned α-calcium-calmodulin-dependent kinase II promoter region was further subcloned into its upstream making use of the AatII recognition sequence and SalI recognition sequence. A plasmid (named pCM-E1 plasmid) having a transgene (12 kb) for use in the preparation of a BEC1-overexpressing transgenic mouse was finally obtained by the above operation.

Example 2 Preparation and Identification of BEC1 Over-expression Transgenic Mouse

The transgene (12 kb) for production. of a BEC1-overexpressing transgenic mouse was cut out from pCM-E1 using restriction enzymes AatII and NotI and then isolated and purified. The thus obtained gene was micro-injected into 283 fertilized eggs of F1 hybrid mice of C57BL/6 and DBA2 mice, and then the resulting fertilized eggs were transplanted into oviducts of ICR foster mother mice (Hogan, B. et al. (1986), Manipulating the mouse embryo: a laboratory manual, Plainview, N.Y.; Cold Harbor Press). The pregnant mice were allowed to undergo spontaneous delivery, and the thus obtained 81 offspring mice were subjected to the identification of transgenic mice.

In order to identify transgenic mice, PCR was carried out using genomic DNA isolated from the tail of each offspring mouse as the template. The genomic DNA was purified from the tail of each mouse using a genomic DNA extraction kit (MagExtractor -Genome-, mfd. by Toyobo). When an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:9 is designed as the forward primer, and an oligonucleotide of the nucleotide sequence represented by SEQ ID NO:10 as the reverse primer, from the BEC1 cDNA (SEQ ID NO:1), and PCR is carried out using them, a 245 bp fragment is amplified from the transgene, and a 338 bp fragment containing 93 bp intron of mouse BEC1 from the mouse genomic DNA. PCR was carried out on the thus obtained baby mouse genomic DNA preparations using these priers. PCR was carried out using a DNA polymerase (AmpliTaq, mfd. by Roche) by employing a thermal denaturation at 94° C. (1 minute) and subsequent repetition of 35 cycles each comprising 94° C. (15 seconds), 60° C. (15 seconds) and 72° C. (30 seconds). The PCR products were subjected to an agarose gel electrophoresis, and DNA was detected by ethidium bromide staining (FIG. 1). As a result, it was identified that 16 of the 81 baby mice are transgenic mice.

Example 3 Determination of BEC1 mRNA

In order to confirm that the introduced gene is actually functioning and BEC1 mRNA is over-expressing, expression of BEC1 mRNA in the brain of transgenic mouse was analyzed. In order to obtain F1 mice for brain extraction use, 11 animals among the 16 transgenic mice were crossed with C57BL/6 mice. As a result, transfer of the transgene to F1 mice was confirmed in 5 transgenic mice. The forebrain and cerebellum were sampled from each of the thus obtained F1 transgenic mice (4-week-old) to isolate respective RNA. Each RNA was digested with a DNase (mfd. by Promega) for the purpose of preventing contamination of genomic DNA. The number of copies of BEC1 mRNA in the thus obtained RNA was determined by a real time PCR using PRISM 7700 (mfd. by ABI) and a fluorescence reagent SYBR Green (mfd. by Molecular Probe). A single-stranded cDNA synthesized from each RNA using a reverse transcriptase-polymerase chain reaction kit (Advantage RT-for-PCR Kit, mfd. by Clontech) was used as the template of the real time PCR. An oligonucleotide of the nucleotide sequence represented by SEQ ID NO:11 was designed as the forward primer, and an oligonucleotide pf the nucleotide sequence represented by SEQ ID NO:12 as the reverse primer, from a sequence common to the transgene, human BEC1, and rat and mouse BEC1.

As a result of the real time PCR, over-expression of forebrain-selective BEC1 mRNA about 10 times higher than that of wild type was found in 3 lines (# 6-5, # 7-7 and # 9-5) among the 5 lines of transgenic mice (FIG. 2). By selecting the line # 9-5, expressed amounts of BEC1 mRNA in respective regions of the brain (cerebral cortex, hippocampus, striatum, hypothalamus, thalamus, mid-brain, brain stem, cerebellum) of wild type mouse were compared with those of the transgenic mouse. As a result, it was confirmed that the BEC1 mRNA over-expression in the transgenic mouse significant in cerebral cortex, hippocampus and striatum in which the expression was also found in the wild type.

Example 4 Analysis of Learned Behavior of BEC1-overexpressing Transgenic Mouse in a Morris Water Maze Test

In order to analyze action of BEC1 overexpression upon learning behavior, learning behavior of # 9-5 line transgenic mice and that of wild type mice in a Morris water maze were compared.

Male 10-week-old transgenic mice (12 animals) and wild type mice (15 animals) were used. A circular pool of 100 cm in diameter was filled with water which had been clouded using paints, and a circular platform of 10 cm in diameter was arranged at a position of 5 mm below the water. Room temperature and water temperature at the time of the test was 23° C. Swimming pattern of each mouse put into the pool was recorded and analyzed by a water maze image analyzer (NIH image, mfd. by O'Hara & CO.), and the escape latency to the platform and the time spent in each quarter area of the pool were measured. One trial of the training was fixed to 70 seconds, and the training was carried out 3 trials per day for 5 days. The escape latency to the platform on the first day of the training was almost the same value in both groups, but the escape latency was prolonged in the transgenic mice than the wild type mice on and after the 3rd day of the start of the training. On the final day of the training, the escape latency to the platform (average value±standard deviation) became 6.9±1.0 seconds in the wild type and 18.1±6.4 seconds in the transgenic mice, thus showing a statistically significant difference (p<0.05: two-way layout analysis of variance).

After completion of the training, each mouse was put for 40 seconds into the pool from which the platform had been removed, and time of the mouse spent in the platform-existed area was measured. As a result, the spent time of transgenic mice was statistically significantly shorter than that of the wild type (p<0.01: Student's t test).

The above results show that learning and memory on the platform position are reduced in the transgenic mice. By this method which uses BEC1 transgenic mice, a substance for antidementia or a substance to improve learning and memory can be screened.

Example 5 Analysis of Learned Behavior of BEC1-overexpressing Transgenic Mouse in a Passive Avoidance Test

Female # 9-5 line transgenic mice (6 animals) and wild type mice (8 animals), 8-week-old, were used. Each mouse was put into the light box region of a light and dark test apparatus for mice (mfd. by O'Hara & Co.), and a constant voltage stimulus of 60 V for 2 seconds was applied to the mouse when it entered the dark box. The mouse was again put into the light box 24 hours thereafter, and the latency to the dark box at this time was measured.

As a result, the latency to the dark box of the transgenic mice was 167 seconds (median) which was significantly short compared to the 600 seconds (median) of the wild type mice (p<0.05: Wilecoxon rank sum test). It was shown that the ability to learn the dark box-related electric stimulus is reduced in the transgenic mice. By this method which uses BEC1 transgenic mice, a substance for antidementia or a substance to improve learning and memory can be screened.

Example 6 Analysis of Anxiety of BEC1-overexpressing Transgenic Mouse by Light and Shade

In order to analyze the action of BEC1 overexpression upon animals, a light/dark exploration test was carried out using # 9-5 line transgenic mice and wild type mice. The light/dark explorationing boxes (mfd. by Muromachi Kikai) comprise a 30 cm square light box and an adjoining dark box of 30 cm×20 cm, and a mouse can freely passes these two boxed through a small hole. Each mouse was put into the exploration boxes for 5 minutes, and the time spent in each box and the number of transitions between the light and dark box were counted by an infrared sensor. As a result, the number of transitions (average value±standard deviation) of the wild type was 14.3±1.5, while it was significantly reduced to 9.4±1.9 in the transgenic mice (p<0.05, Student's t test). Also, the light box staying time was 61.4±4.9 seconds in the wild type, but was 42.4±7.5 seconds in the transgenic mice showing significant reduction (p<0.05, Student's t test). It was shown that anxiety is accelerated in the transgenic mice. By this method which uses BEC1 transgenic mice, a substance for antianxiety can be screened.

Example 7 Analysis of LTP in Hippocampus CA1 of BEC1-overexpressing Transgenic Mouse

It is considered that LTP, a phenomenon in which synaptic transmission efficiency is increased over a long period of time, is a basic process of learning and memory. In order to analyze the action of BEC1 overexpression upon LTP, comparison of LTP in the hippocampus CA1 of # 9-5 line transgenic mice and wild type mice was carried out.

Hippocampus slices were prepared from 5 animals of each of the transgenic mouse and wild type mouse of 3 months of age after birth. Preparation of the hippocampus slices was carried out in accordance with the method of Edwards, F A et al. (1989), “A thin slice preparation for patch clamp recordings from neurons of the mammalian central nervous system”, Pflegers Arch., 414, 600–612. The extracellular electric field potential was recorded using Multi-Electrode Dish (mfd. by Matsushita Electric Industrial, Oka H et al., (1999), J. Neurosci. Methods, 93, 61–67) on which each slice was arranged. The synaptic response of CA1 pyramidal cell was induced by stimulating the Shuffer collateral/comissural fibers —CA1 pathway. In the slice of wild type mouse, tetanus stimulation (100 Hz, 1 second) induced increase of the synaptic reaction (243±26.9% 45 minutes after the tetanus stimulation). On the other hand, similar stimulation induced only a significantly small increase (126±13.6%, p<0.05 by Student's t test) in the slice of transgenic mouse. It was shown that the hippocampus LTP is inhibited in the transgenic mouse.

These results suggest a possibility that BEC1 is causing the impairment in learning and memory by inhibiting formation of the hippocampus LTP. The hippocampus LTP of this transgenic mouse is useful as an index of a substance for antidementia or a substance to improve learning and memory.

Example 8 In Vivo Screening of a Substance for Antidementia or a Substance to Improve Learning and Memory Using Learning and Memory Potassium Channel Inhibitory Action as the Mechanism

In vivo screening of a substance for antidementia or a substance to improve learning and memory using learning and memory potassium channel inhibitory action as the mechanism was carried out by a passive avoidance test similar to Example 5. Each of the compounds to be tested was suspended in 0.5% methyl cellulose physiological saline and intraperitoneally administered 30 minutes before or just after the constant voltage stimulation. The mouse was again put into the light box 24 hours thereafter, and the shaded box-entering time at this time was measured. One compound having the effect to prolong the shaded box-entering time in comparison with the 0.5% methyl cellulose physiological saline-administered group was obtained. It can be judged that this compound has an anti-dementia effect or a learning and memory improving effect.

INDUSTRIAL APPLICABILITY

By the screening method of the present invention, a substance useful as a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety can be in vivo screened.

In vivo screening of a substance for antidementia or a substance to improve learning and memory, which uses the learning and memory potassium channel inhibitory action as the mechanism, can be carried out by using the learning and memory abilities of the transgenic animal of the present invention as the index, and in vivo screening of a substance for antianxiety, which uses the learning and memory potassium channel inhibitory action as the mechanism, can be carried out by using anxiety of the same animal as the index. That is, the transgenic animal of the present invention can be used as a tool for screening a substance for antidementia, a substance to improve learning and memory or a substance for antianxiety.

In addition, a pharmaceutical composition for antidementia, learning and memory improvement use or antianxiety can be produced, using a substance capable of inhibiting the learning and memory potassium channel activity, which can be obtained by the screening method of the present invention, as the active ingredient, and making it into a pharmaceutical preparation using a carrier, a filler and/or other additive agents.

Sequence Listing Free Text

Description on the “Artificial Sequence” is described in the numeral index <223> of the following Sequence Listing. Illustratively, respective nucleotide sequences represented by SEQ ID NOs:3, 6, 7 and 8 in the Sequence Listing are artificially synthesized primer sequences.

Though the present invention has been described in the foregoing based on specific embodiments, modifications and improvements obvious to those skilled in the art are included in the scope of the invention. 

1. A transgenic mouse whose genome comprises a transgene comprising a polynucleotide encoding a potassium channel polypeptide wherein said potassium channel polypeptide comprises the sequence set forth in SEQ ID NO: 2, wherein said polynucleotide is operably linked to a neuronal cell specific promoter, wherein said potassium channel polypeptide is expressed in the brain of said transgenic mouse, and wherein said transgenic mouse exhibits reduced learning and memory abilities, dementia, or anxiety.
 2. The transgenic mouse of claim 1, wherein said promoter is an α-calcium-calmodulin-dependent kinase II promoter.
 3. A method for detecting a substance that inhibits a potassium channel, said method comprising administering a candidate substance to the transgenic mouse of claim 1, measuring anxiety in said transgenic mouse and comparing a change in anxiety to a control mouse.
 4. A method for detecting a substance that inhibits anxiety, said method comprising administering a candidate substance to the transgenic mouse of claim 1, measuring anxiety in said transgenic mouse and comparing a change in anxiety to a control mouse.
 5. A method for screening a substance for anti-anxiety activity, said method comprising administering a candidate substance to the transgenic mouse of claim 1, measuring anxiety in said transgenic mouse, and selecting a substance having an anxiety inhibiting effect. 